LU-14438 ldiskfs: backport ldiskfs mballoc patches

LU-14438 ldiskfs: backport ldiskfs mballoc patches

This contains following kernel patches:

a078dff87013 ("ext4: fixup possible uninitialized variable access in
                     ext4_mb_choose_next_group_cr1()")
80fa46d6b9e7 ("ext4: limit the number of retries after discarding
                     preallocations blocks")
820897258ad3 ("ext4: Refactor code related to freeing PAs")
cf5e2ca6c990 ("ext4: mballoc: refactor
                     ext4_mb_discard_preallocations()")
83e80a6e3543 ("ext4: use buckets for cr 1 block scan instead of
                     rbtree")
a9f2a2931d0e ("ext4: use locality group preallocation for small
                     closed files")
1940265ede66 ("ext4: avoid unnecessary spreading of allocations among
                     groups")
4fca50d440cc ("ext4: make mballoc try target group first even with
                     mb_optimize_scan")
3fa5d23e68a3 ("ext4: reflect mb_optimize_scan value in options file")
077d0c2c78df ("ext4: make mb_optimize_scan performance mount option
                     work with extents")
196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
21175ca434c5 ("ext4: make prefetch_block_bitmaps default")
3d392b2676bf ("ext4: add prefetch_block_bitmaps mount option")
cfd732377221 ("ext4: add prefetching for block allocation bitmaps")
4b68f6df1059 ("ext4: add MB_NUM_ORDERS macro")
dddcd2f9ebde ("ext4: optimize the implementation of
                     ext4_mb_good_group()")
a6c75eaf1103 ("ext4: add mballoc stats proc file")
67d251860461 ("ext4: drop s_mb_bal_lock and convert protected fields
                     to atomic")

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: I079dfb74bd743894934484803cedb683073e4d94